The use of vaccines likely represents the most important, practical contribution that immunologists have made to human health. Effective vaccines establish a state of resistance to microbial diseases in the host prior to infection. Thus, vaccinations function to prevent disease, and such prophylaxis has undoubtedly saved countless lives. In fact, vaccinations have been so successful, that widespread immunizations directed against a variety of bacterial, viral, and parasitic pathogens have become the rule, once an appropriate vaccine has been identified. The most notable example of global immunization was the use of a vaccine against smallpox which eliminated this viral disease.
Ultimately, the success and practicality of widespread immunizations against a particular pathogen depends upon the characteristics of an individual vaccine. These characteristics include: 1) efficacy, i.e. the ability to induce a response that imparts some level of protection in the vast majority of individuals; 2) safety, i.e. limited side effects in immunocompetent children and/or adults; 3) method of delivery, e.g. injectable, oral, intranasal, or transdermal administration; 4) immunization regimen, i.e. single or multiple exposures; 5) stability, i.e., the shelf life and conditions needed for shipping, such as refrigeration; and 6) cost, i.e., the total expense for an immunization regimen, including vaccine production, shipping, and administration. Using these considerations, the most successful vaccines would likely be cheap to produce, highly stable for shipping, and administered in a desirable form that does not require specialized personnel for delivery.
The enormous potential for the use of plant-derived vaccines has been discussed since the first demonstration of the feasibility of such technology in the early 1990s (Mason et al. 1992. Expression of hepatitis B surface antigen in transgenic plants. Proc Natl Acad Sci USA 89:11745, which is herein incorporated by reference in its entirety). An edible vaccine expressed in transgenic plants would represent a cost-effective method for production, as well as the promise of safe administration of an antigen in a highly stable form that could be shipped throughout the world. While the concept of eating a vaccine is easy to visualize, this technology is relatively new. Although some progress has been made toward demonstrating the feasibility of expressing subunit protein antigens in plants, there are drawbacks to the systems methods and use as well as some practical questions concerning the effectiveness of edible vaccines that prior to the instant invention had yet to be addressed.
Despite the promise of plant based vaccines as a low cost method for stimulating mucosal immunity, significant questions still remain about the feasibility of developing such methods for immunizing humans and animals.
Moreover, while widespread vaccination to prevent microbial diseases occurs daily throughout the world, a similar, prophylactic approach has not been used for the widespread prevention of allergic reactions and/or autoimmune antigens. Presently, immunotherapy may be used once an individual has already demonstrated a significant hypersensitivity against a particular allergen or has developed a specific autoimmune disease. However, it has seemed impractical to suggest that it might be feasible to induce tolerance toward specific allergens in individuals even before they demonstrate hypersensitivity.
A criticism for all investigators who have attempted to express vaccines in transgenic plants has been the efficacy and practicality of such immunization strategies. Often the immunogen expressed in plants has had to be purified or significantly concentrated prior to its use as a vaccine. Moreover, often the concentrated or purified plant-derived immunogen must be given parenterally or intranasally to demonstrate its ability to stimulate an immune response.
Soybeans first emerged as a domestic crop in the eastern half of China around the 11th century. Soybeans were later introduced from the Orient to Europe in the early 1700s, and then to North America in the early 1800s. Large scale introduction in the US was in the early 1900s. (from “Soybeans Chemistry, Technology, and Utilization, by KeShun Liu, Aspen Publishers, Inc. Gaithersburg, Md., 1999, ISBN: 0-8342-1299-4). The incorporation of recombinant nucleotide sequences into soybeans first made an appearance in 1988 see Hinchee, et al. 1988. Bio/Technology 6, 915-922. However, to the inventors knowledge, to date, no transgenic soybeans have been used or exploited for antigen production, for soy milk formulations, for use to make adjuvants, for edible vaccines in general, or for any other immunogenic purpose.